Cyculator

Cyculator - The Cyclists calculator.

This software contains 3 formulas that are useful to cyclists.
1) Gear ratio calculator (in inches)
2) Spoke length calculator
3) Vertical dropout chain stay length calculator for bikes with vertical dropouts for those wishing to fit a single (usually fixed) gear.

The gear ratio calculator calculates gear ratios in inches. The wheel size is entered (in inches) and up to 1 to 3 chain rings can be entered and up to 1 to 10 sprockets. Selecting Calc on the menu will then display the ratios.

The spoke length Calculator calculates spoke lengths. First select if the hub is symmetrical (same both sides) or asymmetrical (different both sides. this means that either the flange diameter is different or the center to flange is different or both). Then enter the flange width and center to flange (for both sides if necessary), Rim Diameter and spoke hole diameter. select the number of spokes, the n select calc on the menu. a Table of all the permissible crosses will be displayed. There is a clear option on the menu too. The input region and the result table are scrollable.
The number of available crosses displayed is worked out by dividing the total number of spokes by 9. So a 32 spoke wheel should have a maximum cross of 3, 36 and 40 spoke wheels have a maximum cross of 4, and a 48 spoke wheel has a maximum cross of 5

Vertical dropout chain stay length calculator only deals with the theoretical side of matching a set of sprocket/chain ring combinations to specific length of chain stay.
In practice this is still very difficult to achieve. Firstly it is impossible to measure the chain stays accurately enough to guarantee a match.
Secondly the mathematics assumes that the sprockets and chain rings are perfectly round which unfortunately is frequently not the case, and that the chain has not stretched (1 Link is exactly 1 Inch long).
It will still involve a lot of experimentation to find a working sprocket and chain ring combination.
What this equation allows you to do is once you have found a working combination of any gear (It does not have to be the gear you require). You can then look up other gear ratios that will fit the chain stay length.
Unfortunately it does not guarantee that the gear you desire can be found.
The software enables the user to enter a range of:
1) Chain ring sizes
2) Sprocket sizes
3) Chain stay lengths
4) Desired gears ratios (in inches)
5) Half links

Half links can also be included into the calculations. These can be found for 1/8th chains although they are not commonly used. So by default this option is left unchecked.
If large ranges are entered (particularly chain stay lengths) then it could take a while (around 30 seconds in the worst cases) to calculate results. So I’d advise keeping the chain stay range down to less than half an inch which should be more than enough for the required purpose.

On the results page the following abbreviations are used:
C R - Chain Ring
Spr or Sprock – Sprocket.

The buttons at the bottom of the results page enable you to sort the data by Chain Ring, Sprocket, Gear or chain stay length.

The results screen also shows the number of links in the chain.